Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Mirena (Schering)
intrauterine device containing 52 mg levonorgestrel
Approved indications: contraception, menorrhagia, hormone replacement therapy
Australian Medicines Handbook Section 17.1.2
This product is a T-shaped intrauterine device with a cylinder of levonorgestrel around the long arm. The levonorgestrel is covered by a membrane which controls the release of the drug. At first the release rate is 20 microgram per day. The device contains enough levonorgestrel to last for five years.
The actions of levonorgestrel in the uterine cavity have a contraceptive effect(see 'Progestogen-only methods of contraception' Aust Prescr 1999;22:6-8). Contraceptive protection is immediate because the product also acts as an intrauterine contraceptive device. The contraception is highly effective with a pregnancy rate of 0.16per 100 women years, however 37% of these pregnancies are ectopic.
If there are no organic causes, the device can be used to treat menorrhagia. For some women it is preferable to hysterectomy.1 The device's ability to prevent endometrial hyperplasia also enables it to be used to provide the progestogenic component in regimens of continuous hormone replacement therapy.
Some of the levonorgestrel is absorbed into the circulation and may inhibitovulation. While there are other general effects such as acne, breast tenderness and weight changes, most adverse reactions affect the urogenital system. The menstrual pattern changes with spotting being a particular problem in the first few months after insertion. Increased bleeding or pain may be symptoms that the device is being expelled. The expulsion rate over five years is 2-6 per100. Without the device in place, fertility soon returns. Conception occurs within a year in 80% of the women who have the device removed in order to become pregnant.
Pelvic infection may occur less frequently than with other intrauterine devices, but pelvic inflammatory disease is still a contraindication. The device should be removed if a pelvic infection does not rapidly respond to antibiotics.
While a levonorgestrel-releasing device may have some advantages it is not suitable for all women. It should not be the first choice for contraception in young nulliparous women. The device may also be unsuitable for postmenopausal women if atrophic changes have narrowed the cervical canal.
